Download CHAPTER 18 IV Medication and Titration Calculations

CHAPTER 18 IV MEDICATION AND TITRATION CALCULATIONS
169
CHAPTER 18
IV Medication and Titration Calculations
Objectives
The learner will calculate:
1.
flow rates to infuse ordered dosages.
2.
dosages and flow rates based on kg body weight.
3.
dosage and flow rate ranges for titrated medications.
Suggested Review Questions
1.
How is the dimensional analysis (DA) equation written when calculating IV flow rates if
strength of medication is given and dose per hour or per minute is ordered?
2.
What is the two-step process for using DA to calculate IV flow rates when medication
dosages are ordered by body weight?
3.
What is the one-step process for using DA to calculate IV flow rates when medication
dosages are ordered by body weight?
4.
What does it mean to titrate a medication dose? How are titrated medication doses to be
calculated?
Answers to Review Questions
1.
The DA equation for calculating IV flow rates when strength of medication and dose per
hour are given is
mL/hr = strength of medication present (mL/mg) × rate in mg/hr
=
mL
mg
×
mg
hr
When the dose is specified in amount of drug per minute, the conversion of 60 min = 1 hr
needs to be added to the equation. When the dose per minute or hr is given as a measure
different than the strength of medication provided, the conversion for the measure needs to
also be included in the equation. Therefore, when mL/hr infusion rate is desired for a
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170
SECTION 6 INTRAVENOUS CALCULATIONS
medication dosage of mcg/min and the medication dosage provided is mg/volume of fluid,
the equation is
mL/hr =
2.
mL (volume on hand)
1 mg (dose conversion)
mcg desired
60 min
×
×
×
mg (of drug in vol)
1000 mcg
1min (time to deliver dose)
1 hr
The two-step process for using DA to calculate mL/hr IV flow rates for medications
ordered by body weight is to first calculate the dosage for the patient’s weight and then
proceed with the DA equation. So the patient’s weight in kg is determined, then the
ordered dose per kg. The dosage for the patient’s weight is entered third in the equation as
noted above. Remind students to compute body weight in kg to the nearest tenth and to
calculate IV flow rates of medications to the nearest tenth mL.
3.
The one-step process for using DA to calculate mL/hr IV flow rates for medications
ordered by body weight is to include the dose per patient’s weight conversion in the DA
equation. This does result in a long equation and careful attention must be paid to the entry
of ratios. The patient’s weight is converted to kg (if given in lb) before the patient’s weight
is entered into the equation. The desired dose per kg weight is entered as the third ratio of
the equation with the desired dose as numerator and kg/min as denominator. The patient’s
weight in kg is entered as the numerator in the last ratio of the equation. The equation is:
mL
mL
1 mg
mcg desired
60 min
wt in kg
=
×
×
×
×
hr
mg
1000 mcg
1 min
1 hr
1
4.
To titrate a medication dose is to adjust the medication dose within a specified range to
achieve the physiologic response desired. When a titrated dose of medication is ordered, a
minimum dose and maximum dose are identified. Both of these doses are calculated.
Treatment is initiated using the minimum dose; the dose is then increased as needed, but it
never exceeds the maximum dose unless new medication orders are written. Minimum and
maximum doses are calculated using DA following the equations previously learned.
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CHAPTER 18 IV MEDICATION AND TITRATION CALCULATIONS
171
Name ____________________________________________ Date ____________________
Chapter 18: IV Medication and Titration Calculations
Additional Practice Problems
Calculate the dosages and IV flow rates as requested for the medications below. Round
answers to nearest tenth.
1.
Lidocaine hydrochloride 20 mcg/kg/min has been ordered for a patient with a cardiac
dysrhythmia. The patient weighs 79.5 kg. The solution available is 1 g in 250 mL D5W.
mcg/min dosage
2.
_______________
mL/hr flow rate
_________________
Dopamine hydrochloride has been ordered for a patient who weighs 73.6 kg to maintain
blood pressure. The dosage range is 2 to 5 mcg/kg/min. The solution available is 400 mg
3.
in 500 mL D5W. What is the dosage range for this patient?
_________________
What is mL/hr flow rate to deliver 2 mcg/kg/min?
_________________
Dobutamine has been ordered for a child who weighs 23.6 kg. The ordered dose is
5 mcg/kg/min. Solution available is 250 mg/50 mL of 0.9% NaCl.
mcg/min dosage
4.
______________
mL/hr flow rate
_________________
Nitroglycerin is ordered for a patient with chest pain. The ordered dose is 5 mcg/kg/min to
keep the patient pain free. The patient weighs 61.4 kg. The IV solution available is
nitroglycerin in normal saline at a concentration of 500 mcg/mL.
mcg/min dosage
5.
_______________
mL/hr flow rate
_________________
A dosage of medication is ordered to infuse at 17 mg/hr. The IV solution is prepared at the
concentration of 250 mg of medication in 500 mL of D5W.
mL/hr flow rate
6.
_______________
An IV infusion containing 2 g of medication in 1 L of normal saline is to infuse at 2 to
3 mg/min. What is the mL/hr flow range?
________________
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172
7.
SECTION 6 INTRAVENOUS CALCULATIONS
A dosage of medication at a concentration of 2 g in 500 mL D5W is ordered to infuse at
96 mg/hr.
mL/hr flow rate
8.
________________
The initial dose of a cardiac drug is ordered at 25 mg/hr. The solution was prepared at a
concentration of 125 mg/100 mL of D5W.
mL/hr flow rate
9.
________________
A medication at the dose of 2 mcg/min has been ordered. The solution was prepared at a
concentration of 1 mg in 250 mL of D5W.
mL/hr flow rate
10.
________________
A medication is to be titrated to 10 mcg/kg/min. The IV solution was prepared by adding
250 mg of the medication to 250 mL D5W. The patient weighs 60 kg.
mL/hr flow rate
11.
________________
Epinephrine in D5W is to be run at 2 mcg/min to maintain BP and heart rate. The IV
solution was prepared by adding 2 mg of epinephrine to 250 mL D5W.
mL/hr flow rate
12.
________________
A medication is to be titrated to 150 mcg/kg/min. The IV solution was prepared by adding
2.5 g of medication to 250 mL of D5W. The patient weighs 91.8 kg.
mL/hr flow rate
13.
________________
An initial dose of a cardiac drug is ordered at 25 mg/hr. The solution was prepared by
adding 125 mg of the medication to 100 mL of D5W.
mL/hr flow rate
14.
________________
A medication is ordered to infuse at 40 mcg/kg/min. The patient weights 60 kg. The IV
solution was prepared at a concentration of 1 g of medication in 500 mL D5W.
mL/hr flow rate
________________
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CHAPTER 18 IV MEDICATION AND TITRATION CALCULATIONS
15.
173
The physician ordered aminocarproic acid 30 mg/kg/hr for a child who is bleeding. The
child weighs 27.3 kg. The IV solution has been prepared at a concentration of 5 g of
aminocarproic acid in 250 mL of NS.
mg/hr dose
16.
_______________
mL/hr flow rate
__________________
A medication dosage of 3 mcg/kg/min has been ordered for a patient who weighs 87.3 kg.
The IV solution was prepared at a concentration of 50 mg in 250 mL D5W.
mL/hr flow rate
17.
_______________
Procainamide at the dose of 6 mg/min has been ordered for a patient experiencing
a dysrhythmia. The medication was prepared at a concentration of 1 g procainamide in
250 mL of NS.
mL/hr flow rate
18.
_______________
A medication dosage of 2 mcg/min has been ordered. The medication has been prepared at
a concentration of 1 mg/250 mL D5W.
mL/hr flow rate
19.
_______________
The physician has ordered amiodarone at a dose of 0.5 mg/min. The medication has been
prepared at a concentration of 1g aminodarone to 500 mL of NS.
mL/hr flow rate
20.
_______________
Propofol at the dose of 5 mcg/kg/min has been ordered to maintain sedation for a patient
receiving mechanical ventilation. The patient weighs 84 kg. The medication was prepared
at a concentration of 500 mg in 250 mL of D5W.
mL/hr flow rate
________________
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SECTION 6 INTRAVENOUS CALCULATIONS
Solutions to Additional Practice Problems
Calculate the dosages and IV flow rates as requested for the medications below. Round
answers to the nearest tenth.
1.
mcg/min = 20 mcg/kg/min × 79.5 kg = 1590 mcg/min
Convert 1 g to mg: 1 g = 1000 mg before setting up the DA equation
1
1
1 mg
79.5 kg 4770
mL
250 mL
60 min
=
×
=
×
×
×
hr
200
1 hr
1000 mg
1000 mcg
kg / min
4
20 mcg
50
= 23.85 mL/hr (rounded to the nearest tenth) = 23.9 mL/hr
2.
Lower dosage range = 2 mcg/kg/min × 73.6 kg = 147.2 mcg/min
Upper dosage range = 5 mcg/kg/min × 73.6 kg = 368 mcg/min.
Dosage range is 147.2 to 368 mcg/min.
1
6
1 mg
147.2 mcg
mL
500 mL
60 min
883.2
=
×
=
×
×
hr
1 hr
80
1000 mcg
1 min
400 mg
40
2
= 11.04 mL/hr (rounded to the nearest tenth) = 11 mL/hr
3.
mcg/min = 5 mcg/kg/min × 23.6 kg = 118 mcg/min
1
6
1 mg
118 mcg
mL
50 mL
60 min
780
×
×
=
×
=
hr
1 hr
500
250 mg
1000 mcg
1 min
25
20
= 1.41 mL/hr (rounded to the nearest tenth) = 1.4 mL/hr
4.
mcg/min = 5 mcg/kg/min × 61.4 kg = 307 mcg/min
6
307 mcg
mL
1 mL
60 min
1842
×
=
×
=
hr
1 hr
50
500 mcg
1 min
50
= 36.84 mL/hr (rounded to the nearest tenth) = 36.8 mL/hr
2
5.
17 mg
mL
500 mL
= 34 mL/hr
=
×
1 hr
hr
250 mg
1
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CHAPTER 18 IV MEDICATION AND TITRATION CALCULATIONS
175
1
6.
2 mg
mL
1000 mL
60 min 120
=
×
=
= 60 mL/hr to
×
hr
1 hr
2
2000 mg
1 min
2
1
3 mg
mL
1000 mL
60 min 180
×
=
×
=
= 90 mL/hr
hr
1 hr
2
2000 mg
1 min
2
7.
Convert 1 g to mg: 2 g = 2000 mg before setting up the DA equation
1
96 mg
mL
500 mL
96
×
=
=
= 24 mL/hr
hr
1 hr
4
2000 mg
4
1
8.
25 mg
mL
100 mL
100
×
=
=
= 20 mL/hr
hr
1 hr
5
125 mg
5
1
9.
1 mg
2 mcg
mL
250 mL
60 min 120
×
×
=
×
=
= 30 mL/hr
hr
1 hr
4
1000 mcg
1 min
1 mg
4
1
1
10.
1 mg
10 mcg
60 kg 3600
mL
250 mL
60 min
×
×
×
=
×
=
= 36 mL/hr
1 hr
hr
100
250 mg
1000 mcg
1 kg / min
1
100
1
1
11.
1 mg
2 mcg
mL
250 mL
60 min 60
×
×
=
×
=
= 15 mL/hr
hr
1 hr
4
1000 mcg
1 min
2 mg
1
12.
4
Convert 2.5 g to mg: 2.5 g = 2500 mg before setting up the DA equation
3
1
1 mg
91.8 kg 16,524
mL
250 mL
60 min
×
×
×
=
×
=
1 hr
hr
200
2500 mg
1000 mcg
1 kg / min
10
150 mcg
20
= 82.62 mL/hr (rounded to the nearest tenth) = 82.6 mL/hr
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176
SECTION 6 INTRAVENOUS CALCULATIONS
1
13.
25 mg
mL
100 mL
100
×
=
=
= 20 mL/hr
hr
1 hr
5
125 mg
5
14.
Convert 1 g to mg: 1 g = 1000 mg before setting up the DA equation
1
1
1 mg
60 kg 3600
mL
500 mL
60 min
=
×
=
= 72 mL/hr
×
×
×
hr
50
1 hr
1000 mcg
1 kg / min
1000 mg
2
15.
40 mcg
25
mg/hr = 30 mg/kg/hr x 27.3 kg = 819 mg/hr
Convert 5 g to mg: 5 g = 5000 mg before setting up the DA equation
1
30 mg
mL
250 mL
27.3 kg 819
×
×
=
=
hr
1 hr
20
5000 mg
20
= 40.95 mL/hr (rounded to the nearest tenth) = 41 mL/hr
5
16.
6
1 mg
3 mcg
87.3 kg 7857
mL
250 mL
60 min
=
×
=
×
×
×
hr
100
1 hr
50 mg
1000 mcg
1 kg / min
1
100
= 78.57 mL/hr (rounded to the nearest tenth) = 78.6 mL/hr
1
17.
6 mg
mL
250 mL
60 min 360
×
=
×
=
= 90 mL/hr
hr
1 hr
4
1 min
1000 mg
4
1
18.
1 mg
2 mcg
mL
250 mL
60 min 120
×
×
=
×
=
= 30 mL/hr
hr
1 hr
4
1000 mcg
1 min
1 mg
4
19.
Convert 1g to mg: 1 g = 1000 mg before setting up the DA equation
1
0.5 mg
mL
500 mL
60 min 30
×
=
×
=
= 15 mL/hr
hr
1 hr
2
1 min
1000 mg
2
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CHAPTER 18 IV MEDICATION AND TITRATION CALCULATIONS
1
1
20.
177
1 mg
84 kg 5040
mL
250 mL
60 min
×
×
×
=
×
=
= 12.6 mL/hr
1 hr
hr
200
1000 mcg
1 kg / min
500 mg
2
5 mcg
200
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